[libc][bazel] Add BUILD rules for f16* and *f16 math functions

[vonosmas]

None of the recently added float16 functions are represented in
https://github.com/llvm/llvm-project/blob/main/utils/bazel/llvm-project-overlay/libc/BUILD.bazel. We need to add proper libc_math_functiion rules for them.

[llvmbot]

@llvm/issue-subscribers-libc

Author: Alexey Samsonov (vonosmas)

None of the recently added float16 functions are represented in https://github.com/llvm/llvm-project/blob/main/utils/bazel/llvm-project-overlay/libc/BUILD.bazel. We need to add proper `libc_math_functiion` rules for them.